无法使用Node Streams API，节点驱动程序连接Mongo GridFSBucket

Question

我正在编写一个简单的程序，它将直接从指定的目录处理MP3文件上传进行测试，然后再解析表单数据。现在我遇到了向MongoDB GridFS系统节点驱动程序和节点流API提供适当信息的问题，这将允许我初始化GridFSBucket的实例以开始将文件流式传输到数据库中。 mongo连接从mongoObject.js文件开始，其中插入了一些值以验证数据是否可以流向mLab db，然后该连接将导出整个程序。尝试上传时收到错误

 " _chunksCollection: db.collection(options.bucketName + '.chunks'),  
 TypeError: db.collection is not a function"

感谢您花时间协助，下面是我的代码。

mongoObject.js

var mongodb = require('mongodb'),
    MongoClient = require('mongodb').MongoClient,
    Server = require('mongodb').Server,
    ObjectID = require('mongodb').ObjectID,
    Binary = require('mongodb').Binary,
   // GridStore = require('mongodb').GridStore,
    GridFSBucket = require('mongodb').GridFSBucket,
    Code = require('mongodb').Code,
   // Grid = require('gridfs-stream'),
    gridform = require('gridform'),
    assert = require('assert'),
    mongoURI =  'MLAB-URI-HERE',
    test = require('assert');

const dbName = 'crate';
const testUsername = 'user1';

 module.exports.startup = function(callback) {

  console.log('startup');

   MongoClient.connect(mongoURI, function(err, client) {
       // Create a collection we want to drop later
      const col = client.db(dbName).collection(testUsername);
       // Insert a bunch of documents
      col.insert([{ a: 31, b: 31 }, { a: 13, b: 13 }], { w: 1 }, 
      function(err, result) {
           test.equal(null, err);
           console.log("insert");
       });

       db = client.db(dbName);



   });



}

index.js

const { Readable } = require('stream');

var mongodb = require('mongodb'),
    MongoClient = require('mongodb').MongoClient,
    Server = require('mongodb').Server,
    ObjectID = require('mongodb').ObjectID,
    Binary = require('mongodb').Binary,
   // GridStore = require('mongodb').GridStore,
    GridFSBucket = require('mongodb').GridFSBucket,
    Code = require('mongodb').Code,
   // Grid = require('gridfs-stream'),
    gridform = require('gridform'),
    assert = require('assert'),
    mongoURI =  'MLAB-URI-HERE',
    test = require('assert');


var db = require('./mongoObject.js');


var ct = './ct.mp3';

function upload(db, ct) {


db = db.client.db(dbName);

console.log("starting bucket");
let bucket = new GridFSBucket({
    bucketName: 'user2'
});


const readableTrackStream = new Readable();
readableTrackStream.push(ct);
readableTrackStream.push(null);

let uploadStream = bucket.openUploadStream(ct);
readableTrackStream.pipe(uploadStream)

uploadStream.on('data', (chunk) => {
    console.log('data')
})

uploadStream.on('error', (chunk) => {
    console.log('err');
})

uploadStream.on('end', () => {
    console.log('end');
})

}

upload(db, ct);

package.json依赖项

 "dependencies": {
    "body-parser": "^1.18.2",
    "express": "^4.16.3",
    "express-handlebars": "^3.0.0",
    "formidable": "^1.2.1",
    "gridform": "^0.1.7",
    "gridfs": "^1.0.0",
    "gridfs-stream": "^1.1.1",
    "handlebars": "^4.0.11",
    "mongodb": "^3.0.5",
    "nodemon": "^1.17.2",
    "path": "^0.12.7",
    "stream": "0.0.2",
    "underscore": "^1.8.3"
}